Apparatus and method of forming self-aligned cuts in a non-mandrel line of an array of metal lines

Abstract

A method includes providing a structure having a first hardmask layer, second hardmask layer and mandrel layer disposed respectively over a dielectric stack. An array of mandrels is patterned into the mandrel layer. A gamma trench is patterned into the second hardmask layer and between the mandrels. Self-aligned inner spacers are formed on sidewalls of the gamma trench, the inner spacers forming a portion of a pattern. The pattern is etched into the dielectric stack to form an array of alternating mandrel and non-mandrel metal lines extending in a Y direction and being self-aligned in a perpendicular X direction. The portion of the pattern formed by the inner spacers is utilized to form a pair of non-mandrel line cuts in a non-mandrel line. The non-mandrel line cuts are self-aligned in the Y direction.

What is claimed is: 
     
       1. A method comprising:
 providing a structure having a first hardmask layer, second hardmask layer and mandrel layer disposed respectively over a dielectric stack; 
 patterning an array of mandrels into the mandrel layer; 
 patterning a gamma trench into the second hardmask layer and between the mandrels; 
 forming self-aligned inner spacers on sidewalls of the gamma trench, the inner spacers forming a portion of a pattern; and 
 etching the pattern into the dielectric stack to form an array of alternating mandrel and non-mandrel metal lines extending in a Y direction and being self-aligned in a perpendicular X direction, the portion of the pattern formed by the inner spacers forming a pair of non-mandrel line cuts in a non-mandrel line, the non-mandrel line cuts being self-aligned in the Y direction. 
 
     
     
       2. The method of  claim 1  wherein the non-mandrel line cuts are separated by a center-to-center distance that is 100 nm or less. 
     
     
       3. The method of  claim 1  wherein the non-mandrel line cuts are separated by a center-to-center distance of 50 nm or less. 
     
     
       4. The method of  claim 1  comprising:
 disposing a gamma lithographic stack over the structure; 
 utilizing a single non-mandrel line cut mask to pattern a gamma opening into the gamma lithographic stack; and 
 anisotropically etching the gamma lithographic stack to form the gamma trench into the second hardmask layer. 
 
     
     
       5. The method of  claim 4  wherein the non-mandrel line cuts have an equal width, the method comprising:
 patterning the gamma trench to have a gamma trench width equal to the center-to-center distance between the non-mandrel line cuts plus the width of a non-mandrel line cut. 
 
     
     
       6. The method of  claim 5  comprising:
 disposing a spacer layer over the gamma trench, the spacer layer having a spacer layer thickness; 
 anisotropically etching the spacer layer to form the inner spacers and to expose the first hardmask layer within the gamma trench and between the inner spacers, the inner spacers having a width equal to the thickness of the spacer layer and being separated by an edge-to-edge distance within the gamma trench. 
 
     
     
       7. The method of  claim 6  wherein the inner spacer width is equal to the width of the non-mandrel line cuts and the edge to edge distance between the inner spacers is equal to an edge-to-edge distance between the non-mandrel line cuts. 
     
     
       8. The method of  claim 1  comprising;
 patterning a beta trench into the mandrels; 
 disposing a spacer layer over the structure to form a beta trench plug within the beta trench, the beta trench plug forming a portion of the pattern; and 
 etching the pattern into the dielectric stack to form the array of alternating mandrel and non-mandrel metal lines, the portion of the pattern formed by the beta trench plug forming a mandrel line cut in a mandrel line. 
 
     
     
       9. The method of  claim 8  comprising:
 disposing a beta lithographic stack over the structure; 
 utilizing a single mandrel line cut mask to pattern a beta opening into the beta lithographic stack; and 
 anisotropically etching the beta lithographic stack to form the beta trench into the mandrels. 
 
     
     
       10. A method comprising:
 providing a structure having a first hardmask layer, second hardmask layer and mandrel layer disposed respectively over a dielectric stack; 
 patterning an array of mandrels into the mandrel layer; 
 patterning a beta trench into the mandrels and a gamma trench into the second hardmask layer and between the mandrels; 
 forming self-aligned first and second inner spacers on sidewalls of the gamma trench and plugging the beta trench with a beta trench plug, the inner spacers and beta trench plug forming a portion of a pattern; 
 etching the pattern into the dielectric stack to form an array of alternating mandrel and non-mandrel metal lines extending in a Y direction and being self-aligned in a perpendicular X direction, the portion of the pattern formed by the inner spacers forming a pair of non-mandrel line cuts separated by a center-to-center distance of less than 100 nm in a non-mandrel line, the portion of the pattern formed by the beta trench plug forming a mandrel line cut in a mandrel line. 
 
     
     
       11. The method of  claim 10  wherein the pair of non-mandrel line cuts are self-aligned in the Y direction. 
     
     
       12. The method of  claim 10  wherein the non-mandrel line cuts are separated by a center-to-center distance of 25 nm or less. 
     
     
       13. The method of  claim 10  wherein the non-mandrel line cuts have an equal width, the method comprising:
 patterning the gamma trench to have a gamma trench width equal to the center-to-center distance between the non-mandrel line cuts plus the width of a non-mandrel line cut. 
 
     
     
       14. The method of  claim 10  comprising:
 disposing a spacer layer over the structure after patterning the beta trench and gamma trench, the spacer layer having a substantially uniform spacer layer thickness; and 
 anisotropically etching the spacer layer to form:
 first spacers on sidewalls of the mandrels, 
 the inner spacers on the sidewalls of the gamma trench, 
 an exposed portion of the first hardmask layer within the gamma trench, the exposed portion of the first hardmask layer defining an edge-to edge distance between the first and second inner spacers, and 
 the beta trench plug. 
 
 
     
     
       15. The method of  claim 14  comprising removing the mandrels to form a pattern, the pattern including the first spacers, the inner spacers, the exposed portion of the first hardmask layer within the gamma trench, the beta trench plug and exposed portions of the second hardmask layer between the first spacers. 
     
     
       16. The method of  claim 15  comprising:
 anisotropically etching the pattern into the dielectric stack to form the array of alternating mandrel and non-mandrel metal lines; 
 wherein the metal lines are formed from the exposed portions of the second hardmask layer between the first spacers.